Fluid borne noise generated within a pressurized hydraulic system which uses a pump such as an automotive power steering system, can cause undesired noise and vibration. The oscillating pressure ripples generated by the hydraulic pump are carried within the hydraulic hose and tubing and cause other components to vibrate and emit noise. The use of a tuning tube mounted within a fluid conveyance hose to attenuate these pressure oscillations is known in the art with a description of such of system in U.S. Pat. No. 3,323,305 entitled Attenuation Device and issued to G. Klees on Jun. 6, 1967. The fluid noise reduction structure of the prior art comprises a flexible metal tube, called a tuning cable, that is attached to a hydraulic connector and then placed inside a section of hydraulic hose. The hose is usually permanently attached to the connector by crimping a socket attached to the connector. The tuning cable can incorporate fluid leakage through a corrugated wall and/or the tuning cable can have holes formed along its length to increase the level of attenuation of the pressure pulses and hence, the level of generated noise. The material used for the tuning cable is usually a flexible metal assembly known as a corrugated tube, or it can be made of other similar materials.
The length or other geometry of the tuning cable must be specifically selected to provide the highest level of attenuation depending on the frequencies generated by the pump and the natural vibration frequencies of the various components. Sometimes this can be empirically determined but even then, trial and error is used to determine the exact correct length of the tuning tube along with the location and size of any holes or other apertures along its length. Thus, it would be desirable to have a development system that would permit the tuning tube to be easily changed without building a whole new hose assembly. The prior art systems require that a new hydraulic hose be made each time that the design of the tuning tube is revised which is time consuming and expensive.
The tuning tube can be a corrugated metal wall tube or it can be a tube built up of joined sections with a discontinuous wall construction that results in a distributed leakage along the length of the tuning cable. Or, it can be made of a continuous tube with or of a continuous tube that has apertures formed along its length. The tube can be made of metal or of a suitable plastic material. The fitting used at the end of the hydraulic hose to attach the tuning tube varies depending on the type of material and wall structure that is used for the tuning cable. If the tuning tube is made of a plastic tube material, the tube is commonly slipped over a relatively short barbed tube nipple extending from a hose nipple extension as part of the fitting. The hose is then attached to the fitting using a crimped socket that is mounted on the fitting. Thus, according to the prior art, the length or other design geometry of the tuning tube cannot be changed without destroying the hose assembly. A new assembly with the new tuning tube must be made each time to change the length or other design features of the tuning cable, with is time consuming and expensive.